StudyBlue printing of Chapter Two Newton's 1st Law of Motion-InertiL html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, acronym, address, big, cite, code, del, dfn, em, font, img, ins, kbd, q, s, samp, small, strike, strong, sub, sup, tt, var, b, u, i, center, fieldset, form, label, legend, table, caption, tbody, tfoot, thead, tr, th, td { margin: 0; padding: 0; border: 0; outline: 0; font-size: 100%; background: transparent; } body { line-height: 1; } blockquote, q { quotes: none; } blockquote:before, blockquote:after, q:before, q:after { content: ''; content: none; } /* remember to define focus styles! */ :focus { outline: 0; } /* remember to highlight inserts somehow! */ ins { text-decoration: none; } del { text-decoration: line-through; } /* tables still need 'cellspacing="0"' in the markup */ table { border-collapse: collapse; border-spacing: 0; } /* end RESET */ .header { min-width:800px; } .logo { padding:6px 20px 2px 20px; margin:0; font-size:25px; font-weight:bold; color:#808285; position:relative; border-bottom: 1px solid #c5c5c5; } .logo-blue { color:#70adc4; } .logo-desc { font-weight:normal; font-size:19px; color:#cccccc; margin-top:50px; position:absolute; display: none; } .back-button { position:absolute; top:20px; right:20px; font-size:13px; line-height:25px; color:rgb(0,175,225); font-weight:normal; } .back-button a { color:rgb(0,175,225); } .instructions { padding:0; margin:0; width:100%; position:relative; color:rgb(100,100,100); } .step-holder { border-left:1px solid #ededed; margin-left:20px; } .steps { padding:15px 0; float:left; width:24%; border-right:1px solid #ededed; text-align:center; } .steps-01 { } .steps-02 { } .steps-03 { } .steps-04 { } .label { padding:5px 10px; } .print-button { } .print-button a { background-color:rgb(0,175,225); color:white; line-height: 19px; padding:9px 8px 5px 30px; font-size:14px; text-decoration:none; background-image: url(images/printer.png); background-repeat: no-repeat; background-position: 7px 50%; -moz-border-radius: 5px; -webkit-border-radius: 5px; } .print-button a:hover { background-color:black; } .theNote .content { width: 8.0in !important; margin: 5px auto; padding:20px; background-color:white; } .theNote .header { border-bottom: 1px dashed #C8C8C8; font-size: 17px; padding: 0 0 10px; line-height: 19px; color: #00ADE1; min-width:500px; } .theNote .body { font-size: 14px; line-height: 19px; padding: 10px 0; } .theNote{ padding:6px 0; clear:both; background-color: rgb(200,200,200); } .theNote h3{ color: rgb(100,100,100); } .theNote h1, .theNote h3{ background-color:white; padding:2px 20px; width:8.0in !important; margin: 0 auto; font-size: 15px; } .theNote h1{ padding-top: 10px; font-size: 15px; } .theNote h1:first-child{ font-size: 20px; } .theNote h3 { font-size: 14px; font-weight: normal; } #options { border: 3px double #ccc; padding: 5px 12px; margin: 10px 50px 10px 20px; float: left; } #info { border-top: 1px solid #ccc; padding-top: 5px; font-style: italic; } li { margin: 5px 10px 5px 25px; } ul li { list-style: disc; } ol li { list-style: decimal; } img { border: 0; } table { clear: both; width: 100%; border: 1px solid #c5c5c5; border-width: 1px 0; margin: 0; page-break-after: always; } table#page { page-break-after: auto; } td { text-align: center; font-size: 12px; border-bottom: 1px dashed #c5c5c5; height: 1.75in; width: 50%; padding-left: 15px; } .leftside { border-right: 1px solid #cccccc; padding: 0 15px 0 0; } .bottom td { border-bottom: none; } .clearfix { clear:both; line-height:1px; height:1px; } img { max-width:80%; max-height:150px; margin:20px; } @media print {.header { display: none; } .content .header{ display:inherit; } table { border: 1px dashed #bbb; border-width: 1px 0; } .theNote{ background-color:white; } } CHAPTER TWO A. TERMS
1. Inertia the property of things to resist changes in motion.
2. Force in the simplest sense, a PUSH or a PULL.
3. Mechanical equilibrium is the state of an object or system of objects for
which there are no changes in motion. If at rest, the state of rest persists. If
moving, motion continues without change.
4. Equilibrium rule is for any object or systems of objects in equilibrium, the SUM of the forces acting equal zero, In equation form, EF=0.
B. Review Questions
1. Contrast Aristotle's ideas of natural motion and violent motion.
a. Aristotle divided motion into two main classes; NATURAL MOTION and VIOLENT MOTION.
1. Natural motion could be either straight up or straight down, as in the case of all things on Earth, or it could be circular, as in the case of celstial objects.
a. Unlike up and down motion, circular motion has no beginning or end, repeating itself without deviation.
b. Aristotle believed that different rules apply in the heavens, and he asserted that celestial bodies are perfect spheres made of a perfect and unchanging substance, which he called quintessence.
2. Violent Motion aristotle's other class of motion, resulted from pushing or pulling forces. The essential thing about violent motion was that it was extremely caused and was imparted to objects; they moved not of themselves, not by their "nature", but because of PUSH or PULLS.
a. Violent Motion was IMPOSED MOTION.
b. A person pushing a cart or lifting a heavy weight IMPOSE MOTION, as did hurling a stone or winning a tug of war .
c. The wind imposed motion on ships.
d. Floodwaters imposed it on boulder and tree trunks.
b. Aristotle asserted that natural motion proceeds from the "NATURE" of an object, dependent on what combination of the four elements EARTH, WATER,AIR, and FIRE the object contains
c. In his view, every object in the universe has a proper place, determined by this "nature"; any object not in its proper place will strive to get there.
1. Being of the earth, an unsupported lump of clay properly falls to the ground;
being of the air, an unimpeded puff of smoke properly rises; being a mixture of earth and air but predominantly earth.
2. A feather properly falls to the ground but not as rapidly as a lump of clay.
3. He states the heavier the object would strive harder.
d. Aristotle said objects should fall at speeds proportional to their weights: the heavier the object, the faster it should fall.
e. All motions are due to the nature of the moving object or due to a sustained push or pull.
f. Provided that an objectis in proper place, it will not move unless subject to a forc.
2. What class of motion, natural or violent, did Aristole attribute to motion of the moon?
NATURAL MOTION
a. Aristotle believed that different rules apply in the heavens, he asserted that celestial bodies are perfect spheres made of a perfect and unchanging substance, which he called quintessence.
b. The only celestial object with any detectable variation on its face was the moon. Medieval Christians, still under the somewhat contaminated by the CORRUPTED EARTH.
3. What state of motion did Aristotle attribute to the Earth?
1. Earth must be in its proper place, and since a force capable of moving the Earth was INCONCEIVABLE, it seemed quite clear that the EARTH DOES NOT MOVE.
4. What relationship between the sun and EARTH did COPERNICUS formulate?
a. Copernicus reasoned that the simplest way to account for, the observed motions of the SUN, MOON, and PLANETS through the sky was to asumme that the EARTH CIRCLES THE SUN.
b. He could not reconcile the idea of a moving EARTH with the prevaling ideas of motion.
c. He fear persection so he did not publish his findings until he was on his death bed, MAY 24, 1543
5. What did Galileo discover in his legendary experiment at the LEANING TOWER?
a. Galileo demolsihed Aristotle's falling-body hypothesis. Galileo is said to have dropped objects of various weights from the top of the Leaning Tower of Pisa and compared their falls.
b. Galileo found that a stone twice as heavy as another did not fall twice as fast.
c. Except for the small effect of air resistance, he found that objects of various weights, when released at the same time, fell together and hit the ground at the same time.
6. What did Galileo discover about moving bodies and force in his experiment with inclined planes?
a. Galileo stated that if there is no interference with a moving object , it will keep moving straight line forever, no push, pull, or FORCE of any kind is necessary.
b. He tested this hypothesis by experimenting with the motion of various objects on an inclined planes.
1. He noted that balls rolling on downward-sloping plane PICKUP speed.
2. While balls rolling upward-sloping plane LOST speed
3. Balls rolling along a horizontal plane would neither speedup nor slow down.
4. Balls would finally come to rest not because of its "nature" but because of its friction.
a. Idea is supported by Galileo's observation of motion along smoother surfaces:
b. When there was less friction, the MOTION of objects persisted for a LONGER TIME.
c. LESS FRICTION, the more the motion approach constant speed.
d. In the absence of friction or other opposing forces, a horizontally moving object would continure moving indefinitely.
5. Placed two inclined planes facing each other,
a. Observation was that a ball released from a position of rest at the top of a downward-slopping plane rolled down and then up the slope of the upward sloping plane until it reached its initial height.
b. He reasoned that ONLY FRICTION prevented it from RISING to exactly the same height,for the smoother the plane, the more nearly the ball rose to the same height.
c. He Reduced the angle of the upward sloping plane
1. Ball rose to the same height, but it went further.
2. Additional deductions of the angle yeild similar results. to reach the same height, the ball had to go farther each time.
3. Long horizontal plane, , how far must the ball go to reach the same height, it will never reach its initial height.
d. He analyzed the downward MOTION of the ball from the first plane is the same for all classes,the speed of the ball when it begins moving up the second is the same for all cases.
1. If it moves up a steep slope, it loses its speed rapidly.
2. On the lesser slope, it loses its speed more slowly and rolls for a longer time.
a. less the upward slope, the more slowly it loses its speed.
b. no slope at all ,horizontal the ball should not lose any speed.
c. In the absent of retarded force, the tendency of the ballis to move forever without slowing ndown.
7. What does it mean to say that a moving object has inertia? Give example.
a. The property of an object tending to keep moving straight ahead be called INERTIA.
b. A person rolling down a ski slope.
1. galileo's concept of inertia discredited the aristotelian theory of motion.
a. aristotle did not recognize the idea of inertia because he failed to imagine what motion would be without friction.
b. he said all motion was subject to resistance, and he made this fact central to his theory of motion.
c. Aristotle's failure to recognie friction for what it is -namely, a FORCE LIKE ANY OTHER-impeded the progress of physics for 2000 years, until Galileo.
d. An application of Galileo's concept of inertia would show that NO FORCE IS REQUIRED TO KEEP THE EARTH MOVING FORWARD.
8. Is INERTIA the reason for MOVING OBJECTS maintaining motion, or the name given to this property?
a. In a strict sense, NO
1. We don't know the reason for objects persisting in their motion when no force act on them.
2. We call PROPERTY of material objects to behave in this predictable way INERTIA.
9. Cite Newton's 1st Law of Motion.
a. The tendency of things to RESIST CHANGE in MOTION was what Galileo called INERTIA.
b. Newton REFINED GALILEO IDEA and made it his 1ST LAW, appropriately called the LAW OF INERTIA.
1. Every object continues in its STATE OF REST, or of UNIFORM MOTION in a STRAIGHT LINE, unless it is COMPELLED to CHANGE that state by FORCES IMPRESSED UPON IT.
2. An object CONTINUES to do whatever it happens to be doing unless a FORCE is EXERTED UPON IT.
3. If it is at rest, IT CONTINUES in a STATE OF REST..
4. If an object is MOVING, it CONTINUES TO MOVE without turning or changing speed.
5. Change in MOTION must be imposted against the tendency of an object to retain its STATE OF MOTION.
6. This property of object to RESIST CHANGES in MOTION is called INERTIA.
10. What is the NET FORCE on a CART that is pulled to the right with 100 pounds and to the left with 30 pounds.
a. Change in MOTION are produced by a FORCE or COMBINATION of FORCES.
b. Change in motion is ACCELERATION.
c. A Force is a push or pull.
1. Gavitational
2. Electrical
3. Magnetic
4. Muscular effort.
d. When more than a single force acts on an object, it is called NET FORCE.
1. If more than one force puling in the same direction with equal forces on an object.,
the forces combine to produce a NET FORCE. TWICE as great as your single force.
2. Forces pulling with equal forces in OPPOSITE DIRECTION, NET FORCE is ZERO.
a. Equal but oppositely directed FORCES CANCEL EACH OTHER OUT.
b. One force is consider to be the NEGATIVE OF THE OTHER.
c. they add algebraically to ZERO.
d. With a resulting NET FORCE of ZERO.
1. A PAIR OF 5-LB FORCES in the SAME DIRECTION produces a NET FORCE of
ten lbs .
2. If 5-lb forces are in the OPPOSITE DIRECTION, the NET FORCE is ZERO.
3. 10 lbs are exerted to the RIGHT and 5 lbs to the left
4. The NET FORCE is 5 LBS TO THE RIGHT.
e. If 100 lbs to the right and 30 to the left the NET FORCE is 30 lbs to the RIGHT.
11. Why do we say that FORCE is a VECTOR quantity?
a. A quantity such as FORCE that has BOTH MAGNITUDE and DIRECTION is called a
VECTOR QUANTITY.
12. Can FORCE be EXPRESSED in UNITS of POUNDS and also UNITS of NEWTONS?
a. YES, The 2 lbs is equal to 9 newtons, both lbs and newtons are units of weight, which in turn are units of FORCE.
1. Two Forces
a. Tension Force
b. weight force
2. If the two forces are equal and opposite, and cancel to ZERO
3. Item remains at rest.
b. When the NET FORCE on something is ZERO, it is in aMECHANICAL EQUILIBRIUM.
C. In MATHEMATICAL NOTATION, THE EQUILIBRIUM RULE IS EF=0
13. What is the tension in a rope that is pulled with 100 NEWTONS to the RIGHT and 30 NEWTONS to the LEFT .
14. What is the NET FORCE on a bag pulled down by GRAVITY with 18 NEWTONS?
15. What does it mean to say that something is in mechanical equilibrum?
a. When the NET FORCE on something is ZERO, it is in a MECHANICAL EQUILIBRIUM.
16. State the EQUILIBRIUM RULE in SYMBOLIC NOTATION.
a. The symbol E stands for the VECTOR SUM OF" and F stands for FORCE
b. In MATHEMATICAL NOTATION, the EQUILIBRIUM RULE is EF=0.
c. The rule states:
1. That the FORCE ACTING UPWARD on something at REST MUST BE BALANCE by the other FORCES, ACTING DOWNWARD.
2. To make the VECTOR SUM EQUAL ZERO.
a. Vector quantities take DIRECTION INTO ACCOUNT,
b. So if UPWARD FORCES are +, DOWNWARD ONES are --,
c. When added they actually SUBTRACT .
17. Consider a book that WEIGHS 15 NEWTONS at REST on a FLAT TABLE. How many NEWTONS of SUPPORT FORCE does the TABLE PROVIDE? What is the NET FORCE on the book in thes CASE ?
a. It is in EQUILIBRIUM
b. ONE FORCE is due to GRAVITY-WEIGHT of the BOOK.
c. The book is in EQUILIBRIUM there is another FORCE acting on the book to make the NET FORCE ZERO.
1. An UPWARD FORCE OPPOSITE to the FORCE of GRAVITY
2. TABLE exerts this UPWARD FORCE, called SUPPORT FORCE
3. UPWARD SUPPORT FORCE is called NORMAL FORCE
1. Must EQUAL the WEIGHT of the BOOK
2. UPWARD FORCE POSITIVE
3. DOWNWARD FORCE
18. When you stand at REST on a BATHROOM SCALE, how does your WEIGHT COMPARE with the SUPPORT FORCE by the SCALE?
a. Stepping on a bathroom scale, TWO FORCES ACT on the SCALE.
1. One is DOWNWARD PULL of GRAVITY
2. The other is the UPWARD SUPPORT FORCE of the FLOOR.
a. these FORCES COMPRESS a SPRING that is CALIBRATED to show your WEIGHT.
b. The SCALE show the SUPPORT FORCE.
b. SCALE is at REST, the SUPPORT FORCE and the WEIGHT have the SAME MAGNITUDE.
19. A bowling ball at rest is in equilibrium. Is the ball in equilibrium when it moves at constant speed in a straight-line path?
a. REST is only ONE form of EQUILIBRIUM
b. An object moving at CONSTANT SPEED in a STRAIGHT LINE PATH is also in EQUILIBRIUM.
c. Equilibrium is a STATE of NO CHANGE.
A BOWLING BALL ROLLING at CONSTANT SPEED in a STRAIGHT LINE is also EQUILIBRIUM-until it hits the pins.
d. Whether at rest or steadily rolling in a straight line path, EF=0.
20. What is the test for whether or not a moving object is in equilibrium?
a. By noting whether or not it UNDERGOES CHANGE in its STATE of MOTION.
21. If you PUSH on a CRATE with FORCE of 100 N and it slides at constantly velocity, how much is the FRICTION ACTING on the crate?
a. When the pull on the crate is as great as the FORCE of FRICTION between the CRATE and the floor, the NET FORCE on the CRATE is ZERO and it SLIDES at a UNCHANGING SPEED.
b. If it moves at a STEADY SPEED in a STRAIGHT-LINE PATH , it is in EQUILIBRIUM
c. More than ONE FORCE ACTS on the CRATE.
d, Another FORCE exists-likely the FORCE of FRICTION between the CRATE and the FLOOR.
e. The fact that the NET FORCE on the CRATE EQUALS ZERO means that the FORCE of FRICTION must be EQUAL and OPPOSITE to our PULLING FORCE
22. What CONCEPT was MISSING in people's minds in the SIXTEENTH CENTURY when they couldn't believe the EARTH was MOVING?
a. Not only is the EARTH moving at 30 kilometer persecond, but so are the tree, the branches of the tree, the bird that sits on it, the worm below, and even the air in between
b. All are moving at 30 kilometers per second.
c. Things in motion remain in motion if no unbalanced forces are acting.
23. A bird sitting in a tree is traveling at 30 kms relative to the faraway sun. When the DROPS to the GROUND BELOW, does it still go 30km/s, or does this SPEED BECOME ZERO?
a. So, when the bird drops from the branch, its initial sideway motion of 30 KILOMETERS per second remains UNCHANGED.
b. It cathes the worm quite unaffected by the MOTION OF ITS TOTAL ENVIRONMENT.
24. Stand next to a WALL that TRAVELS at 30 km/s relative to the sun. With your feet on the GROUND you also travel the same 30 km/s. Do you keep this SPEED when your feet leave the ground? What concept supports your answer?
a. Yes, because your are traveling at 30 kilometers per second-before, during, and after the jump.
b. The 30 kilometers per second is the SPEED of the EARTH RELATIVE to the SUN-not the SPEED of the wall relative to you.
25. What did Aristotle fail to RECOGNIZE about the rules of NATURE for OBJECTS on EARTH and in the HEAVENS?
a. Aristotle did not recognize the idea of INERTIA because he did not see that all moving things follow the SAME RULES.
b. He imagined that rules for MOTION in the heavens were very different from the rules of MOTION on EARTH.
c. He saw VERTICAL MOTION as natural, but HORIZONTAL MOTION as UNNATURAL, requiring a SUSTAINED FORCE.
d. Galileo and NEWTON, saw that all moving things follow the SAME RULES.
1. Moving thing require NO FORCE to keep moving if there are NO OPPOSING FORCES, such as FRICTION.